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A Groundwater Flow Model of the Texas Central Coast Constructed from a Detailed Site Conceptual Model

Steven C. Young1, Trevor Budge1, Neil Deeds2, Van Kelley2, Paul Knox3, Ernie Baker4, Geoff Saunders5, and John Waugh6
1 URS, 9400 Amberglen Blvd., Austin, Texas 78729
2 INTERA, Inc., 1812 Centre Creek Dr., Ste. 300, Austin, Texas 78754
3 Baer Engineering and Environmental Consulting, Inc., 7756 Northcross Dr., Ste. 211, Austin, Texas 78757
4 U.S. Geological Survey, Retired, 8027 Exchange Dr., Austin, Texas 78754
5 Lower Colorado River Authority, 3700 Lake Austin Blvd., Austin, Texas 78703
6 San Antonio River System, 2800 U.S. Hwy. 281 N., San Antonio, Texas 78758

A numerical groundwater model covering approximately 10,000 mi2 was constructed for the Central Texas Gulf Coast based on a detailed analysis of data from geophysical logs, river gauges, and well screens. Approximately 650 geophysical well logs were analyzed in conjunction with available aquifer pumping tests to develop algorithms for horizontal hydraulic conductivity, vertical hydraulic conductivity, and specific storage. The locations of the model layers were selected on the basis of a sequence stratigraphic analysis. This analysis showed the need to accurately model a distinctive shallow groundwater system that is hydraulically coupled to surface water features. Model calibration targets for the stream flows were developed from analysis of available river gauge data. The model was calibrated from 1900 to 1997 using approximately 800 hydrographs. Results of the model calibration are compared to results of previous groundwater models. The model comparison shows that the current model has several significant differences in the calibrated values for recharge, groundwater-surface water interaction, and aquifer properties. The authors suggest that one of the key reasons for the differences is that the current model has a more refined vertical layering than previous models. At a regional scale, the vertical layering is important for properly simulating recharge and local-scale groundwater flow in the shallow aquifer system and the impacts of pumping in the deep aquifer system.

 

AAPG Search and Discover Article #90069©2007 GCAGS 57th Annual Convention, Corpus Christi, Texas